The disclosure relates to a pneumatic drive system and a method for operating a pneumatic drive system. The pneumatic drive system is used to actuate a control valve, particularly a regulating valve or a safety valve (emergency shut down (ESD valve)), of a processing plant, such as a petrochemical plant or the like. The pneumatic drive system of the generic type has a pneumatic working chamber and a current/pressure transducer, which is coupled to the working chamber, for loading the working chamber with a pneumatic pressure, by means of which pressure the control valve is moved. The current/pressure transducer has at least one electrical input for receiving an electrical actuating signal.
In many fields of application of the pneumatic drive system of the generic type, it is imperative that a desired position for the control valve is reached rapidly and reliably on the basis of a set-point/actual value regulation. Due to the force transmission by means of pneumatics, the drive system has a tendency to overshoot the set-point position and only to reach the desired position after a delay time.
For example, in the case of the use of the pneumatic drive system in an anti-surge control valve for protecting a compressor, it is imperative that the desired valve position is reached rapidly, wherein a precise position control should be ensured. In order to prevent the undesired operating state of the “pumping” of the compressor, the anti-surge valve should be opened rapidly, so that the output of the compressor can be reduced at the outlet. Overshooting of the anti-surge valve is to be prevented, in order to suppress dangerous operating states of the compressor.
In the case of position control for control valves which are not subjected to frequent operation, it may be the case that the valve member remains adhered on the sealing face of the valve seat. In this case, a larger force must be applied by the pneumatic drive system in order to release the valve member at the valve seat. The delay time incurred in the process makes a rapid and exact regulation problematic. If the control valve is used to regulate a process medium of the processing plant, the control valve has a tendency to vibrate due to excitation by means of the process medium. These vibrations make an exact regulation of the process medium difficult.